FROM: "Dr. A.Routh MD." SUBJECT: Horsepower & Torque DATE: Tue, 01 Jun 1999 10:50:24 -0500 ORGANIZATION: Univ of Miss Medical Center NEWSGROUPS: rec.autos.4x4 I was explaining horsepower & torque to my wife. I said that horsepower is mainly needed for high speed driving like driving in highway at or above 70 mph. The higher the horsepower, higher top speed can be achieved. The torque is mainly for driving at lower speed. So higher the torque, the quicker is getaway from red light. zero to 30 mph depends on torque. Am I right in saying that? With thanks. FROM: w.j.markerink@a1.nl (Willem-Jan Markerink) SUBJECT: Re: Horsepower & Torque DATE: Tue, 01 Jun 99 22:58:52 GMT ORGANIZATION: A1 Internet news-server NEWSGROUPS: rec.autos.4x4 In article <3754013F.AF6C05DA@radiology.umsmed.edu>, "Dr. A.Routh MD." wrote: >I was explaining horsepower & torque to my wife. I said that horsepower >is mainly needed for high speed driving like driving in highway at or >above 70 mph. The higher the horsepower, higher top speed can be >achieved. The torque is mainly for driving at lower speed. So higher the >torque, the quicker is getaway from red light. zero to 30 mph depends on >torque. Am I right in saying that? With thanks. > Horsepower is a product of torque x rpm (x constante). If you know two factors, you can calculate the third. What you are confusing here is maximum horsepower (peak output, where declining torque x increasing rpm has its maximum), vs maximum torque (engine at maximum efficiency), vs torque at any given rpm, especially down low. What makes a car good at the highway, at continuous speed, is maximum horsepower. What makes a car accelerate good is a flat torque band (unless you like shifting, to match those hp maxima to each gear). What makes a car drive good in town is torque at low rpm. If you ever experienced a modern TDi diesel, with a flat (max) torque range from 1400 to way over 3000, then you'll know that torque makes a car drive comfortably (never looking for a gear), while horsepower only makes it drive fast (proper gearing assumed). -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] FROM: Jeff Smith SUBJECT: Re: Horsepower & Torque DATE: Thu, 03 Jun 1999 04:55:54 GMT ORGANIZATION: Deja.com - Share what you know. Learn what you don't. NEWSGROUPS: rec.autos.4x4 Please allow me to put in my two cents: > sbest@TAKEOUTglinx.com (sbest) wrote: > Torque is a force Agreed. > HP is a force over time in distance. Time is not a factor in any measurement of power, such as HP. Whenever you bring time into the equation, you are talking about ENERGY. As an example, one horsepower is equivalent to 746 watts (a watt is a measure of POWER). If you produce 1 horsepower for one hour, you have expended 746 WATT-HOURS (a watt-hour is a measure of ENERGY). For the purposes of discussion, you could also say you have expended one horsepower-hour (I'm not sure if that unit even exists!) It's easy to remember the distinction between power and energy, if you think about your electric bill, which is always in (kilo)watt-hours. Power measured over a period of time. Back to the relationship between torque and power. Torque is simply a force. You don't even have to have motion in order to have torque. Does that sound crazy? Think about the last time you used a torque wrench (the pointer kind). It didn't have to be moving for the needle to still be displaying torque. If you still don't agree, look up torque in the dictionary, then consider this: You're driving a car with an automatic transmission, and you come to a red light. While you're sitting there, with your car not moving, your engine is still delivering torque to your wheels. There's torque applied to your driveshaft, your axles, and your wheels, but nothing's moving, so there's no work being done, no power being delivered. You have torque, but no power. The light turns green, you take your foot off the brake, and the car starts moving. There is still torque being applied; it is the FORCE making the axles turn. Plus, now the force is actually moving a heavy load; you have work being done; you have POWER. Now for an example in the other extreme. Let's say you jack up the drive wheels, start the motor, and put the car in drive. One or both wheels start turning rapidly (diffs are being discussed in OTHER threads, thankfully!). The only drag that has to be overcome in order to produce motion is the friction of the bearings, and the slight drag of the brakes. It's easy to see that very little work is being done here. Despite the fact that the wheels are turning pretty fast, there's not a significant amount of torque being applied, and there's almost no power being used. But, if you step on the brake, the brake shoes and drums start to heat up, right? Now there's work being done, converted into heat, dissipated in the shoes and drums. IT ALWAYS TAKES POWER TO MAKE HEAT. And, if you could measure the driveline torque, you would see that it also increased sharply the moment you stepped on the brakes. In a drivetrain, you can have torque without power, but you can't have power without torque. I guess that's a little more than two cents, huh? -Jeff Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't. FROM: w.j.markerink@a1.nl (Willem-Jan Markerink) SUBJECT: Re: Horsepower & Torque DATE: Fri, 04 Jun 99 01:00:26 GMT ORGANIZATION: A1 Internet news-server NEWSGROUPS: rec.autos.4x4 Jeff Smith wrote in message news:7j18he$srq$1@nnrp2.deja.com... > In article <7j12rm$s5t$12@news.a1.nl>, > w.j.markerink@a1.nl (Willem-Jan Markerink) wrote: > > > > > Horsepower is a product of torque x rpm (x constante). > > So, torque is just a force applied, there doesn't have to be motion, right? Yes. Torque is when two forces twist an object in opposite directions....whether it actually rotates because of that is a different question. > For instance, you can apply all of the available torque of a motor to a > wheel, but if the wheel isn't turning, there's no power, correct? Yes Sir! Just be carefull if one or more *other* wheels are spinning....in that case you are not applying all the available torque from the motor to the wheels. > Or, if one wheel is spinning very fast on an open diff (like it's off the > ground), you still have very little power, because there's very high speed, > but very little torque being used, am I correct? Yes Sir! > So in other words, in a vehicle, power is converted either into motion, or > into heat (smoking tires), right? Yes....just note that 'all power' is a dangerous expression, since that is based on maximum output, and without traction there is no maximum output. -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] FROM: erck@anl.gov (Robert Erck) SUBJECT: Re: Horsepower & Torque DATE: Sat, 05 Jun 1999 11:03:36 -0500 ORGANIZATION: ANL NEWSGROUPS: rec.autos.4x4 In article <3752c2b1.57833460@news.glinx.com>, sbest@TAKEOUTglinx.com (sbest) wrote: > On Fri, 04 Jun 1999 01:41:56 GMT, gribble@primenet.com (Mr. Fun) wrote: > > >I think the easiest way to think of the relationships and meaning of > >torque and hp is..... > > > >Torque determines how MUCH you are going to be able to do. Hp > >determines how FAST you are going to be able to do it. So if you have > >a high torque motor, like a diesel, that's not all that high in terms > >of hp, you will be able to move a big heavy truck OK but you won't get > >it moving very quickly. On the flip side, if you have a light car > >with a relatively low torque engine but with relative high hp output > >it won't be able to "pull" stuff all that well but it will still be > >able to accelerate reasonably well. > > > While I agree in practical experience with what you are saying here, it > is not completely true. Horsepower is horsepower. Whatever torque that is > needed to move a load can be found with gearing IF you have the > horsepower. > > Now, moving a dumptruck with a 200 hp turbo 4cyl with 16 gears and a > 6000 rpm cruise will not be entirely practical, so we look for an engine > that can produce that horsepower in an RPM range that will allow the > engine to last and not drive the driver crazy with gear shifts and revs. > It just so happens an engine that makes 200 hp at 1500 rpm will also make > great gobs of torque down there, due to our little math formula. > > Torque is simply twisting force on an axis. It can be increased or > decreased with gearing or leverage. Hp is the ability to do work (force > times a distance) in a certain amount of time. > > > Steve Best, Nova Scotia, > 4x4 van website: > http://www.glinx.com/users/sbest Steve Best is absolutely correct... Bob ----------------------- FROM: Mike Locke SUBJECT: Re: Horsepower & Torque DATE: Sat, 05 Jun 1999 23:01:55 -0700 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: rec.autos.4x4 Some comments below + my comments regarding engine power vs torque: To make a vehicle move you need power and the right gears. If the power band of the engine is too narrow you will need too many gears and may lose too much performance with time spent shifting. If the power band of the engine is at too high an RPM, the engine may need to be reved excessively and may be unpleasant to drive, hard to control, get poor fuel economy, and/or suffer a short life expectancy. However, the fundamental requirement on your vehicle engine is that it produce enough power to get the task done. Note that torque is not directly involved in the above. Of course you need torque to have power. However, without specifying the RPM of the engine, comparing the torques produced by the engines is meaningless. Power encompases the ability of the engine to get the job done, since it includes the RPM factor. There are other considerations, such as: Can I get the gears needed to get full power out of my engine? Can the engine produce full power continuously? sbest wrote: > > On Thu, 03 Jun 1999 04:55:54 GMT, Jeff Smith > wrote: > > >Please allow me to put in my two cents: > > > >> sbest@TAKEOUTglinx.com (sbest) wrote: > > > >> Torque is a force > > > >Agreed. > > > >> HP is a force over time in distance. > > > >Time is not a factor in any measurement of power, such as HP. Whenever > >you bring time into the equation, you are talking about ENERGY. > > > >As an example, one horsepower is equivalent to 746 watts (a watt is a > >measure of POWER). If you produce 1 horsepower for one hour, you have > >expended 746 WATT-HOURS (a watt-hour is a measure of ENERGY). For the > >purposes of discussion, you could also say you have expended one > >horsepower-hour (I'm not sure if that unit even exists!) > >It's easy to remember the distinction between power and energy, if you > >think about your electric bill, which is always in (kilo)watt-hours. > >Power measured over a period of time. > > I should have known better to get involved with one of these HP-torque > threads! > > Watts and HP are both measures of power, you are correct there, > but HP is indeed a measure of force used to over distance in a given time. > > Old Issac Newton made up this HP thing from an estimate of the power of > a horse. He figured that one horse could lift 550 lbs(force) one > foot(distance) in one second(time). There are too many errors above for me to not jump in. Energy has the same units as work: force * distance Time is not involved. However, energy is often measured as energy = power * time while power = force * distance / time If you substitute the expression for power into the expression for energy, you get energy = force * distance The Horsepower was invented as a standardized unit for measuring the output of steam engines. I believe this definition dates from the early 19th century (100+ years after Newton was buried); IIRC it was done by James Watt (now that sounds too ironic to be right, hmmmm). > Your analogy to your power meter does not work, your power meter > measures the amount of total power used in a unit of hours. You could do > the same with your car if such a meter existed. If your car used on > average 20 HP for the half hour trip to work or back, you could state you > used 100HP/hrs through the week to get to work. A drag racer could also > expend this amount of energy doing 10 10second runs with a 3600hp engine! Regarding electrical power meters: These consist of a cleverly designed electrical motor which converts voltage and amperage into motor RPM (power meter) and then counts motor rotations (energy meter). The gauge shows the count of rotations, so the overall effect is that of a energy meter. -- S'later, Mike Locke karenml@rahul.net or lockem@scrserv.com FROM: "Boerboom" SUBJECT: Re: Paarden krachten en Koppel hoe zit dat nou? DATE: Sun, 29 Aug 1999 03:10:32 +0200 ORGANIZATION: Internet Services at the Horizon NEWSGROUPS: nl.auto koppel(M) = (F)Newton * (A)Meter(kracht maal arm)=arbeid vermogen (P)=(F)Newton *(A)Meter /(t)seconde=arbeid per seconde Als je het toerental van de motor omrekent naar radialen per seconden dan kun je dus vanuit de koppelkromme (grafiek waarin koppel uitgezet is t.o.v. het toerental) de vermogens kromme berekenen. V.B.: Mijn Auto een Ford Taurus 3.8 V6 140 pk(100kW)bij 3800 omw/min 320 Nm bij 2200 omw/min 100 kW=100000Newton Meter per seconde 3800 Omw/min = ong 400 rad/sec <(3800/60)*2pi> koppel bij maximaal vermogen: 100 kW /400 rad/sec=251 Nm omgekeerd: 320 Nm bij 2200 omw/min 2200 omw/min= 2200/60 omw/sec=36,7 omw/sec 1 omwenteling = 2pi radialen 36,7 omw/sec=2pi*36,7 omw/sc=230 rad/sec=hoeksnelheid(omega) P=F*A/t=M/t of M*omega=320*230=74 kW met wat tussenliggende waarden kun je een aardige koppelkromme schetsen. Als je heir wat meer over wilt weten dan moet je in de bieb zoeken bij de werktuigbouwkundige boeken. Bas Boerboom. From: "Mark Schmid" To: <80_series@sgiblab.sgi.com> Subject: Re: Fw: [80] Spec,s Petrol V Diesel Date sent: Mon, 6 Sep 1999 20:37:23 -0700 Organization: PSI Send reply to: 80_series@sgiblab.sgi.com > > Also when measuring horsepower as opposed to Kilowatts you have to take > >into consideration whether you are you are using GC's pony or Norm's > >throughobred or Darren's Draught horse... ;-)) The horsepower > >measurement was started off as a comparison against a standard horse but > >depends what you use a a standard. > 1 hp = 0.7457 kW and 1 hp = 550 ft*lb/s. I don't think there is any other standard to use. Mark Schmid psi@san.rr.com From: Kee Wai Tan To: "'80_series@sgiblab.sgi.com'" <80_series@sgiblab.sgi.com> Subject: RE: Fw: [80] Spec,s Petrol V Diesel Date sent: Tue, 7 Sep 1999 09:50:53 -0000 Organization: Philips PTS Send reply to: 80_series@sgiblab.sgi.com > Also when measuring horsepower as opposed to Kilowatts you have to take >into consideration whether you are you are using GC's pony or Norm's >throughobred or Darren's Draught horse... ;-)) The horsepower >measurement was started off as a comparison against a standard horse but >depends what you use a a standard. Horse power itself as unit of measurement has very well defined meaning. It is the amount of energy (or work) required to raise 33,000 pounds one foot in one minute (or 550 pound-feet per second). It is calculated by multiplying the engine's measured torque by rpm and dividing by 5,252. Basically, given the torque vs rpm chart, we can calculate the horsepower at any given RPM Horse power at the wheels is entirely different story. Cheers Keewai Tan [note WJ] hp = torque x rpm / 5252 1ft-lbs = 1.36Nm pk = koppel x rpm / 7143 FROM: "christo sluijter" SUBJECT: Re: Pk vs Nm DATE: Tue, 1 May 2001 11:29:27 +0200 NEWSGROUPS: nl.auto Vermogen = 2x pi x motordraaimoment x toerental(per sec) Christo FROM: "Thomas Schäfer" SUBJECT: Re: Drehmoment/Leistung DATE: Mon, 22 Apr 2002 10:09:21 +0200 ORGANIZATION: SHE Informationstechnologie AG NEWSGROUPS: de.etc.fahrzeug.auto "Alexander Wunderer" schrieb > Die Leistung eines Motors ist doch direkt proportional zum Drehmoment und > der Drezahl. Nun habe ich gestern die AutoBild durchgeblätert und einen > Vergleichstest gesehen, wo alle 3 Kandidaten ziemlich exakt dieselbe > Leistung bei derselben Drehzahl hatten. Das Drehmoment bei dieser Drehzahl > war aber je nach Kandidat enorm unterschiedlich. Wie bitte geht das? Gar nicht. Leistung = **/30 [note WJ: power (Watt!) = 2 x pi x rpm/sec x torque = pi x rpm/min x torque / 30] [1,333hp = 1000W] Ich habe schon etliche Motordiagramme gesehen, die schlicht und ergreifend falsch waren. Was mich aber an Deiner Beschreibung wundert: Meist wird die max. Leistung bei ihrer Drehzahl angegeben. und das max. Drehmoment (regelmäßig bei deutlich niedrigerer Drehzahl). Dagegen interpretiere ich Deine Frage so, daß auch das Drehmoment bei der Drehzahl max. Leistung angegeben wurde. Das wäre überflüssig (kann man ja nach obiger Formel ausrechnen) und sehr unüblich. MfG Thomas From: "Willem-Jan Markerink" To: fj55@birfield.com Subject: RE: [FJ55] Power/Performance Cc: dtlc@helios.net, landcruisers@birfield.com, 80scool@yahoogroups.com Reply-To: fj55@birfield.com Date: Sat, 05 Apr 2003 21:07:39 +0200 On 5 Apr 2003 at 8:54, Clay Davis wrote: > as best i can tell on a chassis dyno, my particular mostly stock 2F > makes most torque at 1700 rpm, Do you have any data points below that, say 1500/1250/1000/750/500 and perhaps even lower? (most of these dyno's measure 'brake-torque', so in theory they could (should!) go down to a complete stall) > remains pretty smooth only dropping a > bit to 2600rpm then drops off pretty sharp. HP is a steady climb and > hits the top of its curve about 3800 rpm. i had the 36" tires on when > i did this. torque doesnt seem to mind the tires, but i think the > HPdoesnt like them much. i notice while driving especially at hwy > speeds, there is a definite gap when i go to climbing grades, either i > rev it real high in a lower gear or i let it slow and settle in to the > torque, i found something real surprising though, i can pull a 6% > grade over any length at 45 MPH in 4th gear comfortably, wheras i only > get a couple more MPH if i downshift to 3rd and rap the beast out > uncomfortably. I once saw an interesting mathematical approach to this in a German mag....not very complex, but you have recalculate the values of hp- peak and torque-peak....because since you *know* rpm for both, you can calculate torque at hp-peak[*], and then say how much higher torque is at torque-peak, compared to the calculated torque at hp- peak....as a percentage, they called it 'elasticity'....the amount which the torque can 'grow' with by decreasing rpm's, from hp-peak down to torque-peak. And as long as this elasticity is sufficient for the increased load (wind, grade, rolling resistance(trailer)), you don't have to downshift.... [*] hp = torque x rpm x Constant, so if you know 2 of the variables, you can calculate the third. For ft-lbs: hp = torque x rpm / 5252 or torque = hp x 5252 / rpm For Nm (with 1ft-lbs = 1.36Nm) hp = torque x rpm / 7143 or torque = hp x 7143 / rpm (the underlying math for Nm is easier to remember btw: power (in Watt!) = 2 x pi x torque x rpm/sec = 2 x pi x torque x rpm/min / 60 = pi x torque x rpm/min / 30 (1000W = 1.333hp) I think the values for the 2F were 135hp @ 3600rpm and 280Nm @ 1800rpm (206ft-lbs, right?). This means that torque at hp-peak is: torque = hp x 7143 / rpm torque = 135 x 7143 / 3600 = torque = 268Nm (or 197ft-lbs) As a percentage, 280/268 x 100% = 4.5% elasticity (the 'reserve' you have when dropping down in rpm).... Note that this is much more marginal than with most diesels (sample turbodiesel 1HD-T: 167hp@3600rpm & 360Nm@1800Nm and a calculated 331Nm@3600rpm makes 360/331, is about 9%, sample non-TD 2H: 105hp@3500 & 240Nm@1800rpm and a calculated 214Nm@1800Nm makes 240/214, is about 11%). And I have seen even higher numbers of elasticity, but then you get into a range of diesels that are almost agricultural/industrial by nature, torque-houses, dropping even steeper in torque as rpm increases (beyond the torque-peak). -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!]